From 31e6bc5be21461c321f8e07e452eaae4c89e802b Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 22 Aug 1991 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1991-08-22

---
 pc/clock.c   | 34 ----------------------------------
 pc/devuart.c | 12 +++++++-----
 pc/kbd.c     | 19 ++++++++++---------
 pc/trap.c    |  9 +++++++--
 4 files changed, 24 insertions(+), 50 deletions(-)

diff --git a/pc/clock.c b/pc/clock.c
index 2c9aa7ce432cff499d27a4c14dca2ebf79a8a27e..1e03c516f11752f3876d16bccf4dfa7e74181804 100644
--- a/pc/clock.c
+++ b/pc/clock.c
@@ -94,37 +94,3 @@ clock(Ureg *ur)
 		}
 	}
 }
-
-/*
- *  a faster (1 MS) clock tick for a non-interrupting serial port or
- *  kernel profiling.  m->ticks still increments as usual.
- */
-void
-fclock(Ureg *ur)
-{
-	static ulong ticks;
-
-	uartintr0(ur);		/* poll the serial port */
-	if((ticks++ % (FHZ/HZ)) == 0)
-		clock(ur);
-}
-
-void
-fclockinit(void)
-{
-	int x;
-
-	/*
-	 *  set vector for clock interrupts
-	 */
-	setvec(Clockvec, fclock);
-
-	/*
-	 *  make clock output a square wave with a 1/FHZ period
-	 */
-	x = splhi();
-	outb(Tmode, Load0square);
-	outb(T0cntr, (Freq/FHZ));	/* low byte */
-	outb(T0cntr, (Freq/FHZ)>>8);	/* high byte */
-	splx(x);
-}
diff --git a/pc/devuart.c b/pc/devuart.c
index 0d31c6fcfea7d103c7e68fd4bf2ec6cb471df21e..e83e6f88e2481ea8377a502da7065143c276c57e 100644
--- a/pc/devuart.c
+++ b/pc/devuart.c
@@ -36,6 +36,7 @@ enum
 	 Loop=	(1<<4),		/*  loop bask */
 	Lstat=	5,		/* line status */
 	 Inready=(1<<0),	/*  receive buffer full */
+	 Overrun=(1<<1),	/*  we lost an input char */
 	 Outready=(1<<5),	/*  output buffer full */
 	Mstat=	6,		/* modem status */
 	Scratch=7,		/* scratchpad */
@@ -212,6 +213,9 @@ uartintr(Uart *up)
 	IOQ *cq;
 	int s, l;
 
+	/*
+	 *  the for loop takes care of multiple events per interrupt
+	 */
 	for(;;){
 		s = uartrdreg(up, Istat);
 		switch(s){
@@ -229,6 +233,9 @@ uartintr(Uart *up)
 				if(up->delim[ch/8] & (1<<(ch&7)) )
 					wakeup(&cq->r);
 			}
+			l = uartrdreg(up, Lstat);
+			if(l & Overrun)
+				screenputc('!');
 			break;
 	
 		case 2:	/* transmitter empty */
@@ -282,11 +289,6 @@ uartenable(Uart *up)
 			print("can't turn on serial port power\n");
 	}
 
-	/*
-	 *  speed up the clock to poll the uart
-	fclockinit();
-	 */
-
 	/*
 	 *  set up i/o routines
 	 */
diff --git a/pc/kbd.c b/pc/kbd.c
index ee8e37f3501204698894594d3d01e811eb976645..964bf98083b7a9575ba2f47ea388cd59fb3aa5b5 100644
--- a/pc/kbd.c
+++ b/pc/kbd.c
@@ -398,14 +398,6 @@ kbdintr0(void)
 		return 0;
 	}
 
-	keyup = c&0x80;
-	c &= 0x7f;
-	if(c > sizeof kbtab){
-		print("unknown key %ux\n", c|keyup);
-		kbdputc(&kbdq, k1);
-		return 0;
-	}
-
 	/*
 	 *  e0's is the first of a 2 character sequence
 	 */
@@ -417,10 +409,19 @@ kbdintr0(void)
 		return 0;
 	}
 
+	keyup = c&0x80;
+	c &= 0x7f;
+	if(c > sizeof kbtab){
+		print("unknown key %ux\n", c|keyup);
+		kbdputc(&kbdq, k1);
+		return 0;
+	}
+
 	if(esc1){
-print("\nescape1 %lux\n", c);
 		c = kbtabesc1[c];
 		esc1 = 0;
+		kbdputc(&kbdq, c);
+		return 0;
 	} else if(esc2){
 		esc2--;
 		return 0;
diff --git a/pc/trap.c b/pc/trap.c
index 409c93c17a09c695c640d0281ced8755e557a749..3344347bf421d09ed18818f0afbe308726dbaf22 100644
--- a/pc/trap.c
+++ b/pc/trap.c
@@ -190,6 +190,12 @@ trap(Ureg *ur)
 		outb(Int0ctl, EOI);
 	}
 
+	/*
+	 *  check for a waiting character, the uart is at too low
+	 *  a priority level to work correctly at 9600 baud.
+	 */
+	uartintr0(ur);
+
 	/*
 	 *  call the trap routine
 	 */
@@ -264,7 +270,7 @@ syscall(Ureg *ur)
 	u->p->pc = ur->pc;
 	if((ur->cs)&0xffff == KESEL)
 		panic("recursive system call");
-	u->p->insyscall = 0;
+	spllo();
 
 	/*
 	 *  do something about floating point!!!
@@ -274,7 +280,6 @@ syscall(Ureg *ur)
 	sp = ur->usp;
 	u->nerrlab = 0;
 	ret = -1;
-	spllo();
 	if(!waserror()){
 		if(ax >= sizeof systab/BY2WD){
 			pprint("bad sys call number %d pc %lux\n", ax, ur->pc);